Genomic assessment of a multikinase inhibitor, sorafenib, in a rodent model of pulmonary hypertension

Nebulisation of Paclitaxel, Sotatercept and Iloprost for pulmonary hypertension for lung cancer. From In vitro to In vivo

Background: Pulmonary hypertension is common symptom among several diseases. The consequences are severe for several organs. Pulmonary hypertension is usually under-diagnosed and the main symptom observed is dyspnea with or without exercise. Currently we have several treatment modalities administered orally, via inhalation, intravenously and subcutaneously. In advanced disease then heart or lung transplantation is considered. The objective of the study was to investigate the optimum method of aerosol production for the drugs: iloprost, paclitaxel and the novel sotatercept. Materials and Methods: In our experiment we used the drugs iloprost, paclitaxel and the novel sotatercept, in an experimental concept of nebulization. We performed nebulization experiments with 3 jet nebulizers and 3 ultrasound nebulizers with different combinations of residual cup designs, and residual cup loadings in order to identify which combination produces droplets of less than 5μm in mass median aerodynamic diameter. Results: We concluded that paclitaxel cannot produce small droplets and is also still very greasy and possible dangerous for alveoli. However; iloprost vs sotatercept had smaller droplet size formation at both inhaled technologies (1.37<2.23 and 1.92<3.11, jet and ultrasound respectively). Moreover; residual cup designs C and G create the smallest droplet size in both iloprost and sotatercept. There was no difference for the droplet formation between the facemask and cone mouthpieces. Discussion: Iloprost and sotatercept can be administered as aerosol in any type of nebulisation system and they are both efficient with the residual cups loaded with small doses of the drug (2.08 and 2.12 accordingly).

Inhaled nintentanib, pirfenidone and macitentan for pulmonary fibrosis: a laboratory experiment

Aim: Idiopathic pulmonary fibrosis is a rare disease with few efficient drugs in the market. The consequences of this disease are mainly respiratory failure and pulmonary hypertension. Materials & methods: In our experiment we used the drugs pirfenidone, nintetanib and macitentan. We performed nebulization experiments with three jet nebulizers and three ultrasound nebulizers with different combinations of residual cup designs, and residual cup loadings in order to identify which combination produces droplets of less than 5 μm in mass median aerodynamic diameter. Results: Pirfenidone versus nintetanib had smaller droplet size formation at both inhaled technologies (1.37 < 2.23 and 1.92 < 3.11, jet and ultrasound respectively). Discussion: Pirfenidone and nintetanib can be administered as aerosol in any type of nebulization system.

Pathophysiological Involvement of Mast Cells and the Lipid Mediators in Pulmonary Vascular Remodeling

Mast cells are responsible for IgE-dependent allergic responses, but they also produce various bioactive mediators and contribute to the pathogenesis of various cardiovascular diseases, including pulmonary hypertension (PH). The importance of lipid mediators in the pathogenesis of PH has become evident in recent years, as exemplified by prostaglandin I2, the most central therapeutic target in pulmonary arterial hypertension. New bioactive lipids other than eicosanoids have also been identified that are associated with the pathogenesis of PH. However, it remains largely unknown how mast cell-derived lipid mediators are involved in pulmonary vascular remodeling. Recently, it has been demonstrated that mast cells produce epoxidized n-3 fatty acid (n-3 epoxides) in a degranulation-independent manner, and that n-3 epoxides produced by mast cells regulate the abnormal activation of pulmonary fibroblasts and suppress the progression of pulmonary vascular remodeling. This review summarizes the role of mast cells and bioactive lipids in the pathogenesis of PH. In addition, we introduce the pathophysiological role and therapeutic potential of n-3 epoxides, a mast cell-derived novel lipid mediator, in the pulmonary vascular remodeling in PH. Further knowledge of mast cells and lipid mediators is expected to lead to the development of innovative therapies targeting pulmonary vascular remodeling.

Pathophysiology and new advances in pulmonary hypertension

Pulmonary hypertension is a progressive and often fatal cardiopulmonary condition characterised by increased pulmonary arterial pressure, structural changes in the pulmonary circulation, and the formation of vaso-occlusive lesions. These changes lead to increased right ventricular afterload, which often progresses to maladaptive right ventricular remodelling and eventually death. Pulmonary arterial hypertension represents one of the most severe and best studied types of pulmonary hypertension and is consistently targeted by drug treatments. The underlying molecular pathogenesis of pulmonary hypertension is a complex and multifactorial process, but can be characterised by several hallmarks: inflammation, impaired angiogenesis, metabolic alterations, genetic or epigenetic abnormalities, influence of sex and sex hormones, and abnormalities in the right ventricle. Current treatments for pulmonary arterial hypertension and some other types of pulmonary hypertension target pathways involved in the control of pulmonary vascular tone and proliferation; however, these treatments have limited efficacy on patient outcomes. This review describes key features of pulmonary hypertension, discusses current and emerging therapeutic interventions, and points to future directions for research and patient care. Because most progress in the specialty has been made in pulmonary arterial hypertension, this review focuses on this type of pulmonary hypertension. The review highlights key pathophysiological concepts and emerging therapeutic directions, targeting inflammation, cellular metabolism, genetics and epigenetics, sex hormone signalling, bone morphogenetic protein signalling, and inhibition of tyrosine kinase receptors.

Novel p38 Mitogen-Activated Protein Kinase Inhibitor Reverses Hypoxia-Induced Pulmonary Arterial Hypertension in Rats

Mitogen-activated protein kinase (MAPK) signaling is strongly implicated in cardiovascular remodeling in pulmonary hypertension (PH) and right ventricle (RV) failure. The effects of a newly designed p38 inhibitor, LASSBio-1824, were investigated in experimentally induced PH. Male Wistar rats were exposed to hypoxia and SU5416 (SuHx), and normoxic rats were used as controls. Oral treatment was performed for 14 days with either vehicle or LASSBio-1824 (50 mg/kg). Pulmonary vascular resistance and RV structure and function were assessed by echocardiography and catheterization. Histological, immunohistochemical and Western blot analysis of lung and RV were performed to investigate cardiovascular remodeling and inflammation. Treatment with LASSBio-1824 normalized vascular resistance by attenuating vessel muscularization and endothelial dysfunction. In the heart, treatment decreased RV systolic pressure, hypertrophy and collagen content, improving cardiac function. Protein content of TNF-α, iNOS, phosphorylated p38 and caspase-3 were reduced both in lung vessels and RV tissues after treatment and a reduced activation of transcription factor c-fos was found in cardiomyocytes of treated SuHx rats. Therefore, LASSBio-1824 represents a potential candidate for remodeling-targeted treatment of PH.

Reversal of pulmonary arterial hypertension and neointimal formation by kinin B1 receptor blockade

Background

This study examined whether BI113823, a novel selective kinin B1 receptor antagonist can reverse established pulmonary arterial hypertension (PAH), prevent right heart failure and death, which is critical for clinical translation.

Methods

Left pneumonectomized male Wistar rats were injected with monocrotaline to induce PAH. Three weeks later, when PAH was well established, the rats received daily treatment of BI113823 or vehicle for 3 weeks.

Results

Treatment with BI113823 from day 21 to day 42 after monocrotaline injection reversed established PAH as shown by normalized values of mean pulmonary arterial pressure (mPAP). BI113823 therapy reversed pulmonary vascular remodeling, pulmonary arterial neointimal formation, and heart and lung fibrosis, reduced right ventricular pressure, right heart hypertrophy, improved cardiac output, and prevented right heart failure and death. Treatment with BI113823 reduced TNF-α and IL-1β, and macrophages recruitment in bronchoalveolar lavage, reduced CD-68 positive macrophages and expression of proliferating cell nuclear antigen (PCNA) in the perivascular areas, and reduced expression of iNOS, B1 receptors, matrix metalloproteinase (MMP)-2 and MMP-9 proteins, and the phosphorylation of ERK1/2 and AKT in lung. Treatment with BI113823 reduced mRNA expression of ANP, BNP, βMHC, CGTF, collange-I and IV in right heart, compared to vehicle treated controls. In human monocytes cultures, BI113823 reduced LPS-induced TNF-α production, MMP-2 and MMP-9 expression, and reduced TNF-α-induced monocyte migration.

Conclusions

We conclude that BI113823 reverses preexisting severe experimental pulmonary hypertension via inhibition of macrophage infiltration, cytokine production, as well as down regulation of matrix metalloproteinase proteins.

Zinc-mediated activation of CREB pathway in proliferation of pulmonary artery smooth muscle cells in pulmonary hypertension

BACKGROUND

Transcription factor CREB is involved in the development of pulmonary hypertension (PH). However, little is known about the role and regulatory signaling of CREB in PH.

METHODS

A series of techniques, including bioinformatics methods, western blot, cell proliferation and luciferase reporter assay were used to perform a comprehensive analysis of the role and regulation of CREB in proliferation of pulmonary artery smooth muscle cells (PASMCs) in PH.

RESULTS

Using bioinformatic analysis of the differentially expressed genes (DEGs) identified in the development of monocrotaline (MCT)- and hypoxia-induced PH, we found the overrepresentation of CRE-containing DEGs. Western blot analysis revealed a sustained increase in total- and phosphorylated-CREB in PASMCs isolated from rats treated with MCT. Similarly, an enhanced and prolonged serum-induced CREB phosphorylation was observed in hypoxia-pretreated PASMCs. The sustained CREB phosphorylation in PASMCs may be associated with multiple protein kinases phosphorylated CREB. Additionally, hierarchical clustering analysis showed reduced expression of the majority of CREB phosphatases in PH, including regulatory subunits of PP2A, Ppp2r2c and Ppp2r3a. Cell proliferation analysis showed increased PASMCs proliferation in MCT-induced PH, an effect relied on CREB-mediated transcriptional activity. Further analysis revealed the raised intracellular labile zinc possibly from ZIP12 was associated with reduced phosphatases, increased CREB-mediated transcriptional activity and PASMCs proliferation.

CONCLUSIONS

CREB pathway was overactivated in the development of PH and contributed to PASMCs proliferation, which was associated with multiple protein kinases and/or reduced CREB phosphatases and raised intracellular zinc. Thus, this study may provide a novel insight into the CREB pathway in the pathogenesis of PH. Video abstract.

Endothelial eNAMPT drives EndMT and preclinical PH: rescue by an eNAMPT-neutralizing mAb

Pharmacologic interventions to halt/reverse the vascular remodeling and right ventricular dysfunction in pulmonary arterial hypertension (PAH) remains an unmet need. We previously demonstrated extracellular nicotinamide phosphoribosyltransferase (eNAMPT) as a DAMP (damage-associated molecular pattern protein) contributing to PAH pathobiology via TLR4 ligation. We examined the role of endothelial cell (EC)-specific eNAMPT in experimental PH and an eNAMPT-neutralizing mAb as a therapeutic strategy to reverse established PH. Hemodynamic/echocardiographic measurements and tissue analyses were performed in Sprague Dawley rats exposed to 10% hypoxia/Sugen (three weeks) followed by return to normoxia and weekly intraperitoneal delivery of the eNAMPT mAb (1 mg/kg). WT C57BL/6J mice and conditional EC-cNAMPTec-/- mice were exposed to 10% hypoxia (three weeks). Biochemical and RNA sequencing studies were performed on rat PH lung tissues and human PAH PBMCs. Hypoxia/Sugen-exposed rats exhibited multiple indices of severe PH (right ventricular systolic pressure, Fulton index), including severe vascular remodeling, compared to control rats. PH severity indices and plasma levels of eNAMPT, IL-6, and TNF-α were all significantly attenuated by eNAMPT mAb neutralization. Compared to hypoxia-exposed WT mice, cNAMPTec-/- KO mice exhibited significantly reduced PH severity and evidence of EC to mesenchymal transition (EndMT). Finally, biochemical and RNAseq analyses revealed eNAMPT mAb-mediated rectification of dysregulated inflammatory signaling pathways (TLR/NF-κB, MAP kinase, Akt/mTOR) and EndMT in rat PH lung tissues and human PAH PBMCs. These studies underscore EC-derived eNAMPT as a key contributor to PAH pathobiology and support the eNAMPT/TLR4 inflammatory pathway as a highly druggable therapeutic target to reduce PH severity and reverse PAH.

Novel Experimental Therapies for Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive and devastating disease characterized by pulmonary artery vasoconstriction and vascular remodeling leading to vascular rarefaction with elevation of pulmonary arterial pressures and pulmonary vascular resistance. Often PAH will cause death from right heart failure. Current PAH-targeted therapies improve functional capacity, pulmonary hemodynamics and reduce hospitalization. Nevertheless, today PAH still remains incurable and is often refractory to medical therapy, underscoring the need for further research. Over the last three decades, PAH has evolved from a disease of unknown pathogenesis devoid of effective therapy to a condition whose cellular, genetic and molecular underpinnings are unfolding. This article provides an update on current knowledge and summarizes the progression in recent advances in pharmacological therapy in PAH.

A proteome signature of umbilical cord serum associated with congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a congenital anomaly characterized by a defect in the diaphragm. Despite the recent improvements in its treatment, CDH is associated with a high rate of neonatal mortality, which is often related to pulmonary hypoplasia (PH) as well as pulmonary hypertension. A better understanding of the underlying pathological mechanisms of PH in CDH could help establish a new treatment to improve its prognosis. In this study, we investigated serum biological profiles in neonates with CDH. For comprehensive investigation, umbilical cord serum samples were collected from isolated CDH cases (n = 4) and matched healthy controls (n = 4). Samples were analyzed using liquid chromatography–tandem mass spectrometry. A total of 697 proteins were detected; of them, 98 were identified as differentially expressed proteins. Among these differentially expressed proteins, complement C1q subcomponent showed the largest fold change, followed by complement C5. In the pathway enrichment analysis, the complement and coagulation cascades expressed the most significant enrichment (p = 2.4 × 10⁻²⁶). Thus, the complement pathway might play some role in the pathophysiology of CDH.

Therapeutic Potential of Regorafenib-A Multikinase Inhibitor in Pulmonary Hypertension

Pulmonary hypertension (PH) is characterized by a progressive elevation of mean arterial pressure followed by right ventricular failure and death. Previous studies have indicated that numerous inhibitors of receptor tyrosine kinase signaling could be either beneficial or detrimental for the treatment of PH. Here we investigated the therapeutic potential of the multi-kinase inhibitor regorafenib (BAY 73-4506) for the treatment of PH. A peptide-based kinase activity assay was performed using the PamStation^®12 platform. The 5-bromo-2′-deoxyuridine proliferation and transwell migration assays were utilized in pulmonary arterial smooth muscle cells (PASMCs). Regorafenib was administered to monocrotaline- and hypoxia-induced PH in rats and mice, respectively. Functional parameters were analyzed by hemodynamic and echocardiographic measurements. The kinase activity assay revealed upregulation of twenty-nine kinases in PASMCs from patients with idiopathic PAH (IPAH), of which fifteen were established as potential targets of regorafenib. Regorafenib showed strong anti-proliferative and anti-migratory effects in IPAH-PASMCs compared to the control PASMCs. Both experimental models indicated improved cardiac function and reduced pulmonary vascular remodeling upon regorafenib treatment. In lungs from monocrotaline (MCT) rats, regorafenib reduced the phosphorylation of c-Jun N-terminal kinase and extracellular signal-regulated kinase 1/2. Overall, our data indicated that regorafenib plays a beneficial role in experimental PH.

Divergent changes of p53 in pulmonary arterial endothelial and smooth muscle cells involved in the development of pulmonary hypertension

The tumor-suppressive role of p53, a transcription factor that regulates the expression of many genes, has been linked to cell cycle arrest, apoptosis, and senescence. The noncanonical function or the pathogenic role of p53 has more recently been implicated in pulmonary vascular disease. We previously reported that rapid nuclear accumulation of hypoxia-inducible factor (HIF)-1α in pulmonary arterial smooth muscle cells (PASMCs) upregulates transient receptor potential channels and enhances Ca²⁺ entry to increase cytosolic Ca²⁺ concentration ([Ca²⁺]_cyt). Also, we observed differences in HIF-1α/2α expression in PASMCs and pulmonary arterial endothelial cells (PAECs). Here we report that p53 is increased in PAECs, but decreased in PASMCs, isolated from mice with hypoxia-induced pulmonary hypertension (PH) and rats with monocrotaline (MCT)-induced PH (MCT-PH). The increased p53 in PAECs from rats with MCT-PH is associated with an increased ratio of Bax/Bcl-2, while the decreased p53 in PASMCs is associated with an increased HIF-1α. Furthermore, p53 is downregulated in PASMCs isolated from patients with idiopathic pulmonary arterial hypertension compared with PASMCs from normal subjects. Overexpression of p53 in normal PASMCs inhibits store-operated Ca²⁺ entry (SOCE) induced by passive depletion of intracellularly stored Ca²⁺ in the sarcoplasmic reticulum, while downregulation of p53 enhances SOCE. These data indicate that differentially regulated expression of p53 and HIF-1α/2α in PASMCs and PAECs and the cross talk between p53 and HIF-1α/2α in PASMCs and PAECs may play an important role in the development of PH via, at least in part, induction of PAEC apoptosis and PASMC proliferation.

TGF-β and BMPR2 Signaling in PAH: Two Black Sheep in One Family

Knowledge pertaining to the involvement of transforming growth factor β (TGF-β) and bone morphogenetic protein (BMP) signaling in pulmonary arterial hypertension (PAH) is continuously increasing. There is a growing understanding of the function of individual components involved in the pathway, but a clear synthesis of how these interact in PAH is currently lacking. Most of the focus has been on signaling downstream of BMPR2, but it is imperative to include the role of TGF-β signaling in PAH. This review gives a state of the art overview of disturbed signaling through the receptors of the TGF-β family with respect to vascular remodeling and cardiac effects as observed in PAH. Recent (pre)-clinical studies in which these two pathways were targeted will be discussed with an extended view on cardiovascular research fields outside of PAH, indicating novel future perspectives.

Effects of toceranib compared with sorafenib on monocrotaline-induced pulmonary arterial hypertension and cardiopulmonary remodeling in rats

Sorafenib reverses pulmonary arterial hypertension (PAH) and cardiopulmonary remodeling (CPR), but the effects of toceranib are unknown. This study investigated anti-remodeling effects and determined optimal doses of toceranib and sorafenib on monocrotaline (MCT)-induced PAH and CPR in rats. MCT-treated rats were orally treated with a 14-day course of sorafenib (10, 30, or 100 mg/kg), toceranib (1, 3, or 10 mg/kg), or water. Both sorafenib and toceranib significantly reversed the right ventricular (RV) hypertrophy at 10 mg/kg, but only sorafenib significantly improved the RV systolic and mean pressures. Sorafenib significantly normalized the B-type natriuretic peptide mRNA level of the RV and increased the non-muscularized pulmonary artery percentage. However, these effects were only observed at the highest toceranib dose, and neither toceranib dose reduced the fully muscularized pulmonary artery percentage. Further, the inhibition on vascular endothelial growth factor (VEGF) signaling was stronger in sorafenib than in toceranib. Besides the stronger inhibition on mitogen-activated protein kinase signaling, the greater reversal ability of sorafenib may be also due to the simultaneous blockade on the C-X-C chemokine receptor type 4 and autophagy induction. Toceranib insignificantly reversed CPR, and a high-dose therapy did not improve the RV hemodynamic outcomes. Sorafenib significantly reversed CPR, and a low-dose sorafenib therapy may be a suitable therapeutic agent for PAH.

The aryl hydrocarbon receptor is required for induction of p21cip1/waf1 expression and growth inhibition by SU5416 in hepatoma cells

The aryl hydrocarbon receptor (AhR) is a potential clinical target for cancer and autoimmune dysfunction. Identifying selective AhR modulators that produce desirable clinical outcomes represents an opportunity for developing new anti-cancer agents. Repurposing clinically-used drugs with established safety profiles that activate the AhR represents a good starting place to pursue this goal. In this study, we characterized the AhR-dependent effects of SU5416 (Semaxanib) following its identification in a small-molecule library screen. SU5416 potently activated AhR-dependent reporter genes, induced AhR nuclear localization, facilitated AhR-DNA binding, and increased, expression of its endogenous target genes. SU5416 significantly inhibited proliferation of Hepa1 hepatoma cells in an AhR-dependent manner, but did not induce apoptosis. SU5416 also inhibited the growth of human HepG2 liver cancer cells. The effects of SU5416 correlated with an increased G1 population and increased expression of cell cycle inhibitor p21^cip1/waf1 at both the mRNA and protein level. Increased expression of p21^cip1/waf1 by SU5416 required expression of both AhR and Arnt. In addition, evidence for long-term activation of the AhR in vivo by a single dose of SU5416 was identified by analyzing published microarray data. Our results provide support for continued investigation of the AhR as therapeutic for cancers such as hepatocellular carcinoma. In addition, our findings raise the possibility that some of the previously observed anti-proliferative effects of SU5416 may be due to activation of the AhR.

Sorafenib as a potential strategy for refractory pulmonary arterial hypertension

Sorafenib is an inhibitor of multi-kinases including tyrosine and serine/threonine kinases. We investigated the efficacy and safety of sorafenib for the treatment of patients with refractory pulmonary arterial hypertension (PAH). Sorafenib was started in 9 patients (7 with idiopathic PAH, 2 with pulmonary veno-occlusive disease) who had severe PAH and right heart failure, in spite of treatment with vasodilators specific for PAH. Sorafenib was started as an add-on therapy at a dose of 50 or 100 mg/day, and increased to 100-400 mg/day. New York Heart Association functional class improved in 8 patients and did not change in 1. Mean pulmonary arterial pressure improved in 6 patients (14-28% decrease) and did not apparently change in 2 (follow-up catheterization was not performed in 1 patient). The main adverse effects of sorafenib were skin reactions on the hands and feet, which appeared in 5 patients. They were tolerable in 4 patients, but discontinuation of sorafenib was needed in only 1 patient. In conclusion, sorafenib had favorable effects to improve symptoms and objective variables in patients with refractory PAH, with tolerable adverse events. Sorafenib is an alternative strategy for patients with refractory PAH.

Comparative Transcriptome Analysis Identifies CCDC80 as a Novel Gene Associated with Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a heterogeneous disorder associated with a progressive increase in pulmonary artery resistance and pressure. Although various therapies have been developed, the 5-year survival rate of PAH patients remains low. There is thus an important need to identify novel genes that are commonly dysregulated in PAH of various etiologies and could be used as biomarkers and/or therapeutic targets. In this study, we performed comparative transcriptome analysis of five mammalian PAH datasets downloaded from a public database. We identified 228 differentially expressed genes (DEGs) from a rat PAH model caused by inhibition of vascular endothelial growth factor receptor under hypoxic conditions, 379 DEGs from a mouse PAH model associated with systemic sclerosis, 850 DEGs from a mouse PAH model associated with schistosomiasis, 1598 DEGs from one cohort of human PAH patients, and 4260 DEGs from a second cohort of human PAH patients. Gene-by-gene comparison identified four genes that were differentially upregulated or downregulated in parallel in all five sets of DEGs. Expression of coiled-coil domain containing 80 (CCDC80) and anterior gradient two genes was significantly increased in the five datasets, whereas expression of SMAD family member six and granzyme A was significantly decreased. Weighted gene co-expression network analysis revealed a connection between CCDC80 and collagen type I alpha 1 (COL1A1) expression. To validate the function of CCDC80 in vivo, we knocked out ccdc80 in zebrafish using the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system. In vivo imaging of zebrafish expressing a fluorescent protein in endothelial cells showed that ccdc80 deletion significantly increased the diameter of the ventral artery, a vessel supplying blood to the gills. We also demonstrated that expression of col1a1 and endothelin-1 mRNA was significantly decreased in the ccdc80-knockout zebrafish. Finally, we examined Ccdc80 immunoreactivity in a rat PAHmodel and found increased expression in the hypertrophied media and adventitia of the pre-acinar pulmonary arteries (PAs) and in the thickened intima, media, and adventitia of the obstructed intra-acinar PAs. These results suggest that increased expression of CCDC80 may be involved in the pathogenesis of PAH, potentially by modulating the expression of endothelin-1 and COL1A1.

PDGF induces SphK1 expression via Egr-1 to promote pulmonary artery smooth muscle cell proliferation

Pulmonary arterial hypertension (PAH) is a progressive, life-threatening disease for which there is currently no curative treatment available. Pathologic changes in this disease involve remodeling of the pulmonary vasculature, including marked proliferation of pulmonary artery smooth muscle cells (PASMCs). Recently, the bioactive lipid sphingosine-1-phosphate (S1P) and its activating kinase, sphingosine kinase 1 (SphK1), have been shown to be upregulated in PAH and promote PASMC proliferation. The mechanisms regulating the transcriptional upregulation of SphK1 in PASMCs are unknown. In this study, we investigated the role of platelet-derived growth factor (PDGF), a PAH-relevant stimuli associated with enhanced PASMC proliferation, on SphK1 expression regulation. In human PASMCs (hPASMCs), PDGF significantly increased SphK1 mRNA and protein expression and induced cell proliferation. Selective inhibition of SphK1 attenuated PDGF-induced hPASMC proliferation. In silico promoter analysis for SphK1 identified several binding sites for early growth response protein 1 (Egr-1), a PDGF-associated transcription factor. Luciferase assays demonstrated that PDGF activates the SphK1 promoter in hPASMCs, and truncation of the 5'-promoter reduced PDGF-induced SphK1 expression. Stimulation of hPASMCs with PDGF induced Egr-1 protein expression, and direct binding of Egr-1 to the SphK1 promoter was confirmed by chromatin immunoprecipitation analysis. Inhibition of ERK signaling prevented induction of Egr-1 by PDGF. Silencing of Egr-1 attenuated PDGF-induced SphK1 expression and hPASMC proliferation. These studies demonstrate that SphK1 is regulated by PDGF in hPASMCs via the transcription factor Egr-1, promoting cell proliferation. This novel mechanism of SphK1 regulation may be a therapeutic target in pulmonary vascular remodeling in PAH.

The Effect of Sorafenib, Tadalafil and Macitentan Treatments on Thyroxin-Induced Hemodynamic Changes and Cardiac Abnormalities

Multikinase inhibitors (e.g. Sorafenib), phosphodiesterase-5 inhibitors (e.g. Tadalafil), and endothelin-1 receptor blockers (e.g. Macitentan) exert influential protection in a variety of animal models of cardiomyopathy; however, their effects on thyroxin-induced cardiomyopathy have never been investigated. The goal of the present study was to assess the functional impact of these drugs on thyroxin-induced hemodynamic changes, cardiac hypertrophy and associated altered responses of the contractile myocardium both in-vivo at the whole heart level and ex-vivo at the cardiac tissue level. Control and thyroxin (500 μg/kg/day)-treated mice with or without 2-week treatments of sorafenib (10 mg/kg/day; I.P), tadalafil (1 mg/kg/day; I.P or 4 mg/kg/day; oral), macitentan (30 and 100 mg/kg/day; oral), and their vehicles were studied. Blood pressure, echocardiography and electrocardiogram were non-invasively evaluated, followed by ex-vivo assessments of isolated multicellular cardiac preparations. Thyroxin increased blood pressure, resulted in cardiac hypertrophy and left ventricular dysfunction in-vivo. Also, it caused contractile abnormalities in right ventricular papillary muscles ex-vivo. None of the drug treatments were able to significantly attenuate theses hemodynamic changes or cardiac abnormalities in thyroxin-treated mice. We show here for the first time that multikinase (raf1/b, VEGFR, PDGFR), phosphodiesterase-5, and endothelin-1 pathways have no major role in thyroxin-induced hemodynamic changes and cardiac abnormalities. In particular, our data show that the involvement of endothelin-1 pathway in thyroxine-induced cardiac hypertrophy/dysfunction seems to be model-dependent and should be carefully interpreted.

Microarray analysis in pulmonary hypertension

Microarrays are a powerful and effective tool that allows the detection of genome-wide gene expression differences between controls and disease conditions. They have been broadly applied to investigate the pathobiology of diverse forms of pulmonary hypertension, namely group 1, including patients with idiopathic pulmonary arterial hypertension, and group 3, including pulmonary hypertension associated with chronic lung diseases such as chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis. To date, numerous human microarray studies have been conducted to analyse global (lung homogenate samples), compartment-specific (laser capture microdissection), cell type-specific (isolated primary cells) and circulating cell (peripheral blood) expression profiles. Combined, they provide important information on development, progression and the end-stage disease. In the future, system biology approaches, expression of noncoding RNAs that regulate coding RNAs, and direct comparison between animal models and human disease might be of importance.

Comprehensive overview of compartment-specific microarray studies of material from pulmonary hypertension patientshttp://ow.ly/YEFO2

Raf/ERK drives the proliferative and invasive phenotype of BMPR2-silenced pulmonary artery endothelial cells

A proliferative endothelial cell phenotype, inflammation, and pulmonary vascular remodeling are prominent features of pulmonary arterial hypertension (PAH). Bone morphogenetic protein type II receptor (BMPR2) loss-of-function is the most common cause of heritable PAH and has been closely linked to the formation of pathological plexiform lesions. Although some BMPR2 mutations leave ligand-dependent responses intact, the disruption of ligand-independent, noncanonical functions are universal among PAH-associated BMPR2 genotypes, but incompletely understood. This study examined the noncanonical signaling consequences of BMPR2 silencing in human pulmonary artery endothelial cells to identify potential therapeutic targets. BMPR2 siRNA silencing resulted in a proliferative, promigratory pulmonary artery endothelial cell phenotype and disruption of cytoskeletal architecture. Expression profiling closely reflected these phenotypic changes. Gene set enrichment and promoter analyses, as well as the differential expression of pathway components identified Ras/Raf/ERK signaling as an important consequence of BMPR2 silencing. Raf family members and ERK1/2 were constitutively activated after BMPR2 knockdown. Two Raf inhibitors, sorafenib and AZ628, and low-dose nintedanib, a triple receptor tyrosine kinase inhibitor upstream from Ras, reversed the abnormal proliferation and hypermotility of BMPR2 deficiency. Inhibition of dysregulated Ras/Raf/ERK signaling may be useful in reversing vascular remodeling in PAH.

Novel Targets of Drug Treatment for Pulmonary Hypertension

Biomedical advances over the last decade have identified the central role of proliferative pulmonary arterial smooth muscle cells (PASMCs) in the development of pulmonary hypertension (PH). Furthermore, promoters of proliferation and apoptosis resistance in PASMCs and endothelial cells, such as aberrant signal pathways involving growth factors, G protein-coupled receptors, kinases, and microRNAs, have also been described. As a result of these discoveries, PH is currently divided into subgroups based on the underlying pathology, which allows focused and targeted treatment of the condition. The defining features of PH, which subsequently lead to vascular wall remodeling, are dysregulated proliferation of PASMCs, local inflammation, and apoptosis-resistant endothelial cells. Efforts to assess the relative contributions of these factors have generated several promising targets. This review discusses recent novel targets of therapies for PH that have been developed as a result of these advances, which are now in pre-clinical and clinical trials (e.g., imatinib [phase III]; nilotinib, AT-877ER, rituximab, tacrolimus, paroxetine, sertraline, fluoxetine, bardoxolone methyl [phase II]; and sorafenib, FK506, aviptadil, endothelial progenitor cells (EPCs) [phase I]). While substantial progress has been made in recent years in targeting key molecular pathways, PH still remains without a cure, and these novel therapies provide an important conceptual framework of categorizing patients on the basis of molecular phenotype(s) for effective treatment of the disease.

Macitentan reverses early obstructive pulmonary vasculopathy in rats: early intervention in overcoming the survivin-mediated resistance to apoptosis

It remains unknown whether current disease-targeting therapy can histologically reverse obstructive pulmonary vasculopathy and how the timing of the therapy influences the antiremodeling effects of the compound. We test the hypothesis that a novel endothelin receptor antagonist macitentan reverses the early and/or late stages of occlusive pulmonary vascular disease (PVD) in rats. Rats with pulmonary arterial hypertension (PAH), which were produced by combined exposure to a vascular endothelial growth factor receptor inhibitor Sugen 5416 and hypobaric hypoxia for 3 wk, were assigned to receive macitentan or vehicle during 3-5 wk (early study) or during 5-8 wk (late study) after Sugen injection. Compared with vehicle-treated PAH rats and PAH rats evaluated before treatment initiation, the macitentan-treated rats showed decreases in the proportion of occlusive lesions in the early study, a finding consistent with the reversal of right ventricular systolic pressure and indexes of right ventricular hypertrophy and medial wall thickness. Macitentan ameliorated but did not reverse the proportion of occlusive lesions in the late study. Although macitentan decreased the proportion of Ki67+ lesions in both studies, macitentan increased the proportion of cleaved caspase 3+ lesions and suppressed an antiapoptotic molecule survivin expression in the early study but not in the late study. In conclusion, macitentan reversed early but not late obstructive PVD in rats. This reversal was associated with the suppression of survivin-related resistance to apoptosis and proliferation of cells in PVD.

Inhaled tyrosine kinase inhibitors for pulmonary hypertension: a possible future treatment

Pulmonary hypertension is a disease with severe consequences for the human body. There are several diseases and situations that induce pulmonary hypertension and are usually underdiagnosed. Treatments include conventional medical therapies and oral, inhaled, intravenous, and subcutaneous options. Depending on its severity, heart or lung transplant may also be an option. A possible novel treatment could be tyrosine kinase inhibitors. We conducted experiments with three jet nebulizers and three ultrasound nebulizers with erlotinib, gefitinib, and imatinib. Different residual cup designs and residual cup loadings were used in order to identify the best combination to produce droplets of less than 5 μm in mass median aerodynamic diameter. We found that gefitinib could not be transformed into a powder, so conversion to an aerosol form was not possible. Our experiments indicated that imatinib is superior to erlotinib with regard to small droplet size formation using both inhaled technologies (1.37 μm <2.23 μm and 1.92 μm <3.11 μm, jet and ultrasound, respectively) and, at jet devices (1.37 μm <1.92 μm). Cup designs C and G contribute best to small droplet creation uniquely supporting and equally well the activity of both drugs. The disadvantage of the large droplets formed for erlotinib was offset when combined with residual cup C (1.37 μm instead of 2.23 μm). At a 2 mL dose, the facemask and cone mouthpieces performed best and evenly; the facemask and low dose were the best choice (2.08 μm and 2.12 μm, respectively). Erlotinib and imatinib can be administered as an aerosols, and further in vivo experimentation is necessary to investigate the positive effects of these drugs in the treatment of pulmonary hypertension.

Novel mechanisms of sildenafil in pulmonary hypertension involving cytokines/chemokines, MAP kinases and Akt

Pulmonary arterial hypertension (PH) is associated with high mortality due to right ventricular failure and hypoxia, therefore to understand the mechanism by which pulmonary vascular remodeling initiates these processes is very important. We used a well-characterized monocrotaline (MCT)-induced rat PH model, and analyzed lung morphology, expression of cytokines, mitogen-activated protein kinase (MAPK) phosphorylation, and phosphatidylinositol 3-kinase-Akt (PI-3k-Akt) pathway and nuclear factor (NF)-κB activation in order to elucidate the mechanisms by which sildenafil's protective effect in PH is exerted. Besides its protective effect on lung morphology, sildenafil suppressed multiple cytokines involved in neutrophil and mononuclear cells recruitment including cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-2α/β, tissue inhibitor of metalloproteinase (TIMP)-1, interleukin (IL)-1α, lipopolysaccharide induced CXC chemokine (LIX), monokine induced by gamma interferon (MIG), macrophage inflammatory protein (MIP)-1α, and MIP-3α. NF-κB activation and phosphorylation were also attenuated by sildenafil. Furthermore, sildenafil reduced extracellular signal-regulated kinase (ERK)1/2 and p38 MAPK activation while enhanced activation of the cytoprotective Akt pathway in PH. These data suggest a beneficial effect of sildenafil on inflammatory and kinase signaling mechanisms that substantially contribute to its protective effects, and may have potential implications in designing future therapeutic strategies in the treatment of pulmonary hypertension.

Saudi Guidelines on the Diagnosis and Treatment of Pulmonary Hypertension: Pulmonary arterial hypertension associated with connective tissue diseases

The explosive growth of medical literature on pulmonary hypertension (PH) has led to a steady increase in awareness of this disease within the medical community during the past decade. The recent revision of the classification of PH is presented in in the main guidelines.

Group 1 PH or pulmonary arterial hypertension (PAH) is a heterogeneous group and includes PH due to inheritable, drug-induced, and toxin-induced causes and to such underlying systemic causes as connective tissue diseases, human immunodeficiency viral infection, portal hypertension, congenital heart disease, and schistosomiasis.

Systemic sclerosis (SSc) is an autoimmune multisystem disorder, which affects over 240 persons per million in the United States.[1] Its manifestations are not confined to the skin but may also involve the lungs, kidneys, peripheral circulation, musculoskeletal system, gastrointestinal tract, and heart.

The outcome of PAH associated with SSc is worse when compared to other subtypes of PAH.

In this review, we summarize available information about the pulmonary vascular and cardiac manifestations of SSc with special emphasis on their prognostic implications as well as the peculiarity of their detection.

STAT3 signaling in pulmonary arterial hypertension

Pulmonary artery hypertension (PAH) is a proliferative disorder associated with enhanced pulmonary artery smooth muscle cell proliferation and suppressed apoptosis. The sustainability of this phenotype requires the activation of pro-survival transcription factor like the signal transducers and activators of transcription-3 (STAT3). Using multidisciplinary and translational approaches, we and others have demonstrated that STAT3 activation in both human and experimental models of PAH accounts for the modulation of the expression of several proteins already known as implicated in PAH pathogenesis, as well as for signal transduction to other transcription factors. Furthermore, recent data demonstrated that STAT3 could be therapeutically targeted in different animal models and some molecules are actually in clinical trials for cancer or PAH treatment.

Multikinase inhibitor sorafenib prevents pressure overload-induced left ventricular hypertrophy in rats by blocking the c-Raf/ERK1/2 signaling pathway

Background

Left ventricular hypertrophy (LVH) is a potent risk factor for sudden death and congestive heart failure.

Methods

We tested the effect of sorafenib, a multikinase inhibitor (10 mg/kg, given orally, starting 2 days prior to banding, till sacrifice on day 14), on the development of LVH following aortic banding in rats.

Results

The latter resulted in significant LVH caused by both an increase in cardiomyocyte volume and interstitial collagen deposition. The observed LVH was entirely blocked by sorafenib downregulating both of these components. LVH was associated with PDGF-BB and TGFβ1 overexpression, as well as phosphorylation of c-raf and ERK1/2. Additionally, the transcription factors c-myc and c-fos leading to proliferation as well as the hypertrophy-inducing transcription factor GATA4 and its regulated gene ANP were all upregulated in response to aortic banding. All these overexpressions and upregulations were inhibited upon sorafenib treatment.

Conclusion

We show that sorafenib exhibits a regulatory role on the occurrence of LVH following AB in rats by blocking the rise in growth factors PDGF-BB and TGFβ1, activation of the corresponding c-Raf-ERK1/2 signaling pathway and effector mechanisms, including GATA4 and ANP. This effect of sorafenib may be of clinical importance in modulating the maladaptive hypertrophic response to pressure overload.

Novel medical therapies for pulmonary arterial hypertension

Available targeted therapies for pulmonary arterial hypertension are capable only of slowing progression of the disease and a cure remains elusive. However with the improved understanding of the pulmonary vascular remodeling that characterizes the disease, there is optimism that the disconnect between preclinical and clinical studies may be bridged with some of the newer therapies that are now at different stages of clinical evaluation. This article examines the evidence behind these new candidate treatments that may become part of the arsenal available for clinicians managing this devastating disease.

Therapies for scleroderma-related pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH), a common complication of systemic sclerosis, carries a very severe prognosis and is one of the leading causes of death in patients who suffer from it. Indeed, response to modern medical therapy has been disappointing in scleroderma-related PAH compared with other forms of PAH from the WHO group 1 classification of diseases, despite similar histological changes involving the pulmonary vasculature. This review discusses specific features of scleroderma-related PAH, currently available and US FDA-approved therapy for this syndrome, as well as potential future therapeutic developments based on newly acquired knowledge of this disorder.

PGC1α-mediated mitofusin-2 deficiency in female rats and humans with pulmonary arterial hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is a lethal, female-predominant, vascular disease. Pathologic changes in PA smooth muscle cells (PASMC) include excessive proliferation, apoptosis-resistance, and mitochondrial fragmentation. Activation of dynamin-related protein increases mitotic fission and promotes this proliferation-apoptosis imbalance. The contribution of decreased fusion and reduced mitofusin-2 (MFN2) expression to PAH is unknown.

OBJECTIVES

We hypothesize that decreased MFN2 expression promotes mitochondrial fragmentation, increases proliferation, and impairs apoptosis. The role of MFN2's transcriptional coactivator, peroxisome proliferator-activated receptor γ coactivator 1-α (PGC1α), was assessed. MFN2 therapy was tested in PAH PASMC and in models of PAH.

METHODS

Fusion and fission mediators were measured in lungs and PASMC from patients with PAH and female rats with monocrotaline or chronic hypoxia+Sugen-5416 (CH+SU) PAH. The effects of adenoviral mitofusin-2 (Ad-MFN2) overexpression were measured in vitro and in vivo.

MEASUREMENTS AND MAIN RESULTS

In normal PASMC, siMFN2 reduced expression of MFN2 and PGC1α; conversely, siPGC1α reduced PGC1α and MFN2 expression. Both interventions caused mitochondrial fragmentation. siMFN2 increased proliferation. In rodent and human PAH PASMC, MFN2 and PGC1α were decreased and mitochondria were fragmented. Ad-MFN2 increased fusion, reduced proliferation, and increased apoptosis in human PAH and CH+SU. In CH+SU, Ad-MFN2 improved walking distance (381 ± 35 vs. 245 ± 39 m; P < 0.05); decreased pulmonary vascular resistance (0.18 ± 0.02 vs. 0.38 ± 0.14 mm Hg/ml/min; P < 0.05); and decreased PA medial thickness (14.5 ± 0.8 vs. 19 ± 1.7%; P < 0.05). Lung vascularity was increased by MFN2.

CONCLUSIONS

Decreased expression of MFN2 and PGC1α contribute to mitochondrial fragmentation and a proliferation-apoptosis imbalance in human and experimental PAH. Augmenting MFN2 has therapeutic benefit in human and experimental PAH.

Anticipated classes of new medications and molecular targets for pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) remains a life-limiting condition with a major impact on the ability to lead a normal life. Although existing therapies may improve the outlook in some patients there remains a major unmet need to develop more effective therapies in this condition. There have been significant advances in our understanding of the genetic, cell and molecular basis of PAH over the last few years. This research has identified important new targets that could be explored as potential therapies for PAH. In this review we discuss whether further exploitation of vasoactive agents could bring additional benefits over existing approaches. Approaches to enhance smooth muscle cell apotosis and the potential of receptor tyrosine kinase inhibition are summarised. We evaluate the role of inflammation, epigenetic changes and altered glycolytic metabolism as potential targets for therapy, and whether inherited genetic mutations in PAH have revealed druggable targets. The potential of cell based therapies and gene therapy are also discussed. Potential candidate pathways that could be explored in the context of experimental medicine are identified.

The role of disturbed blood flow in the development of pulmonary arterial hypertension: lessons from preclinical animal models

Pulmonary arterial hypertension (PAH) is a progressive pulmonary vasoproliferative disorder characterized by the development of unique neointimal lesions, including concentric laminar intima fibrosis and plexiform lesions. Although the histomorphology of neointimal lesions is well described, the pathogenesis of PAH and neointimal development is largely unknown. After three decades of PAH pathobiology research the focus has shifted from vasoconstriction towards a mechanism of cancer-like angioproliferation. In this concept the role of disturbed blood flow is seen as an important trigger in the development of vascular remodeling. For instance, in PAH associated with congenital heart disease, increased pulmonary blood flow (i.e., systemic-to-pulmonary shunt) is an essential trigger for the occurrence of neointimal lesions and PAH development. Still, questions remain about the exact role of these blood flow characteristics in disease progression. PAH animal models are important for obtaining insight in new pathobiological processes and therapeutical targets. However, as for any preclinical model the pathophysiological mechanism and clinical course has to be comparable to the human disease that it mimics. This means that animal models mimicking human PAH ideally are characterized by: a hit recognized in human disease (e.g., altered pulmonary blood flow), specific vascular remodeling resembling human neointimal lesions, and disease progression that leads to right ventriclular dysfunction and death. A review that underlines the current knowledge of PAH due to disturbed flow is still lacking. In this review we will summarize the current knowledge obtained from PAH animal models associated with disturbed pulmonary blood flow and address questions for future treatment strategies for PAH.

Adenosine A2A receptor-dependent proliferation of pulmonary endothelial cells is mediated through calcium mobilization, PI3-kinase and ERK1/2 pathways

Hypoxia and HIF-2α-dependent A2A receptor expression and activation increase proliferation of human lung microvascular endothelial cells (HLMVECs). This study was undertaken to investigate the signaling mechanisms that mediate the proliferative effects of A2A receptor. A2A receptor-mediated proliferation of HLMVECs was inhibited by intracellular calcium chelation, and by specific inhibitors of ERK1/2 and PI3-kinase (PI3K). The adenosine A2A receptor agonist CGS21680 caused intracellular calcium mobilization in controls and, to a greater extent, in A2A receptor-overexpressing HLMVECs. Adenoviral-mediated A2A receptor overexpression as well as receptor activation by CGS21680 caused increased PI3K activity and Akt phosphorylation. Cells overexpressing A2A receptor also manifested enhanced ERK1/2 phosphorylation upon CGS21680 treatment. A2A receptor activation also caused enhanced cAMP production. Likewise, treatment with 8Br-cAMP increased PI3K activity. Hence A2A receptor-mediated cAMP production and PI3K and Akt phosphorylation are potential mediators of the A2A-mediated proliferative response of HLMVECs. Cytosolic calcium mobilization and ERK1/2 phosphorylation are other critical effectors of HLMVEC proliferation and growth. These studies underscore the importance of adenosine A2A receptor in activation of survival and proliferative pathways in pulmonary endothelial cells that are mediated through PI3K/Akt and ERK1/2 pathways.

Sorafenib treatment improves hepatopulmonary syndrome in rats with biliary cirrhosis

HPS (hepatopulmonary syndrome) is characterized by oxygen desaturation in patients with chronic liver disease. The initiation of HPS comes from abnormal pulmonary vasodilatation and/or angiogenesis. In the present study, we evaluated anti-angiogenesis therapy using sorafenib in experimental HPS animals. HPS was induced by CBDL (common bile duct ligation) in rats. A 2-week 10 mg·(kg of body weight)-1·day-1 treatment regimen of sorafenib or distilled water (control) was initiated 2 weeks after the surgical procedure. Haemodynamics, liver biochemistry, plasma VEGF (vascular endothelial growth factor) measurements and blood gas analysis of the CBDL rats were performed. The livers of the CBDL rats were dissected for histopathology examination, and the lungs were examined by immunohistochemical staining, real-time PCR and Western blot analysis. In another two parallel groups, intrapulmonary shunts were determined. The AaPO2 (alveolar-arterial O2 gradient) and plasma VEGF levels were reduced after sorafenib treatment [AaPO2, 7.2±3.4 mmHg in sorafenib-treated rats compared with 15.3±4.2 mmHg in controls (P=0.004); VEGF, 45.3±2.7 pg/ml in sorafenib-treated rats compared with 54.4±7.7 pg/ml in controls (P=0.021)]. Sorafenib attenuated pulmonary VEGF mRNA and VEGF, VEGFR-2 (VEGF receptor 2), phospho-VEGFR-2 and Akt protein expression. In addition, sorafenib significantly attenuated intrapulmonary angiogenesis and decreased the degree of intrapulmonary shunting by 33.7% (11.2±5.7% in sorafenib-treated rats compared with 16.9±5.9% in controls; P=0.003). Our findings suggest that sorafenib attenuates intrapulmonary shunting and decreases the AaPO2 in CBDL rats, implicating the improvement of HPS in this experimental animal model. The beneficial effect may be attributed to the reduction in intrapulmonary angiogenesis through inhibition of the VEGF/VEGFR-2/Akt pathway.

Gene expression analysis of a murine model with pulmonary vascular remodeling compared to end-stage IPAH lungs

Background

Idiopathic pulmonary arterial hypertension (IPAH) continues to be one of the most serious intractable diseases that might start with activation of several triggers representing the genetic susceptibility of a patient. To elucidate what essentially contributes to the onset and progression of IPAH, we investigated factors playing an important role in IPAH by searching discrepant or controversial expression patterns between our murine model and those previously published for human IPAH. We employed the mouse model, which induced muscularization of pulmonary artery leading to hypertension by repeated intratracheal injection of Stachybotrys chartarum, a member of nonpathogenic and ubiquitous fungus in our envelopment.

Methods

Microarray assays with ontology and pathway analyses were performed with the lungs of mice. A comparison was made of the expression patterns of biological pathways between our model and those published for IPAH.

Results

Some pathways in our model showed the same expression patterns in IPAH, which included bone morphogenetic protein (BMP) signaling with down-regulation of BMP receptor type 2, activin-like kinase type 1, and endoglin. On the other hand, both Wnt/planar cell polarity (PCP) signaling and its downstream Rho/ROCK signaling were found alone to be activated in IPAH and not in our model.

Conclusions

Activation of Wnt/PCP signaling, in upstream positions of the pathway, found alone in lungs from end stage IPAH may play essential roles in the pathogenesis of the disease.

Pulmonary arterial hypertension in connective tissue diseases

Pulmonary arterial hypertension (PAH) may complicate diverse connective tissue diseases (CTDs). Approximately 10% of patients with systemic sclerosis develop PAH, the prevalence being much lower in other CTDs. However, PAH is an important contributor to morbidity and mortality in all forms of CTD. Despite similarities in presentation, hemodynamic perturbations, and pathogenesis, patients with CTD-associated PAH (CTD-PAH) usually have a poorer response to PAH-specific medications and poorer prognosis than patients with idiopathic PAH (IPAH). Select patients with CTD-PAH may be candidates for lung transplantation, but results are less favorable than for IPAH because of comorbidities and complications specifically associated with CTD.

Sorafenib is effective in the treatment of pulmonary veno-occlusive disease

The present study is the first report of the effectiveness of sorafenib in the treatment of pulmonary veno-occlusive disease (PVOD). A 66-year-old woman with PVOD was started on sorafenib. After 3 months of treatment with a maximum dosage of 400 mg/day sorafenib, there was an improvement in the patient's New York Heart Association (NYHA) functional class from IV to III. However, because of severe painful eruptions as a side effect of sorafenib, the patient stopped sorafenib and was started on imatinib instead. This treatment resulted in a worsening of the patient's NYHA class from III to IV, so sorafenib was restarted at a reduced dosage of 300 mg/day. The resumption of sorafenib was associated with clinical improvement, specifically NYHA class from IV to II and hemodynamic amelioration, and tolerable eruptions. In conclusion, sorafenib may be a potential therapeutic strategy for the treatment of PVOD.

Tyrosine kinase inhibitor (TKI)-induced cardiotoxicity: approaches to narrow the gaps between preclinical safety evaluation and clinical outcome

Although therapies targeted to inhibit the activity of certain tyrosine kinases (TK) have helped advance cancer therapy in recent years, reports of cardiac toxicity following treatment with tyrosine kinase inhibitors (TKIs) were unexpected and not well predicted by preclinical studies. Such clinical findings exposed gaps in current preclinical drug testing for predicting the development of cardiac toxicities in humans. These gaps included a lack of a comprehensive TKI mechanism of action determination and appropriate cardiac functional evaluation. New preclinical approaches are suggested to address these issues. In addition to tyrosine kinase inhibition, other factors that may play a role in drug-induced cardiac effects should be assessed, such as unintended secondary targets of TKIs, toxic drug metabolites and drug accumulation in the heart. Both on-target and off-target toxic effects of TKIs on cultured cardiac myocytes have now been shown to be detectable, providing a rationale for using cardiomyocytes as a screening tool to study potential TKI-mediated cardiotoxicity. Incorporating isolated perfused heart methodology to chronic/subchronic rodent studies or including echocardiography in chronic large animal toxicity studies may improve the detection of changes in cardiac function over current methods, and they may eventually become a routine tool for screening drugs with suspected cardiotoxic potential. Further, assessing drug toxicity and efficacy together in an animal model of disease is highly informative for candidate drug selection, and should be encouraged to assess specific safety endpoints, such as cardiovascular function. Together, these approaches will help better close the gaps between preclinical testing and clinical outcomes.

RAF-targeted therapy for hepatocellular carcinoma in the regenerating liver

BACKGROUND

Post-operative liver regeneration may contribute to tumor recurrence. There is a theoretical need for an adjuvant therapy that can suppress tumor growth without adversely affecting post-operative liver regeneration.

OBJECTIVE

To evaluate the effect of RAF inhibitor Sorafenib on cell viability and proliferation of hepatoma cells and hepatocytes in vitro and in an in vivo rat model.

METHODS

Cell viability, DNA synthesis, and RAF/MAPK kinase activity in the primary hepatocyte and hepatoma cell lines were investigated after Sorafenib exposure. Sequence analysis of the B-RAF gene in hepatic cells was determined. Tumor markers were compared within the rats after 70% hepatectomy with or without daily oral gavages of Sorafenib. Liver regeneration was assessed by liver function tests and proliferation markers.

RESULTS

Primary hepatocytes showed higher cell viability, proliferation rate, and stronger RAF/MAPK kinase activity compared with hepatoma cell lines. The in vivo tumor volumes, size, and metastases were significantly decreased (P < 0.05) whereas no significant change in liver regeneration related to Sorafenib exposure was found (P > 0.05). B-RAF V600E mutation was not detected neither in the hepatic cells nor untransformed hepatocytes.

CONCLUSIONS

The RAF targeted inhibitor can reduce tumor growth without retarding liver regeneration in this experiment.

A novel molecular signature for elevated tricuspid regurgitation velocity in sickle cell disease

RATIONALE

An increased tricuspid regurgitation jet velocity (TRV > 2.5 m/s) and pulmonary hypertension defined by right heart catheterization both independently confer increased mortality in sickle cell disease (SCD).

OBJECTIVES

We explored the usefulness of peripheral blood mononuclear cell-derived gene signatures as biomarkers for an elevated TRV in SCD.

METHODS

Twenty-seven patients with SCD underwent echocardiography and peripheral blood mononuclear cell isolation for expression profiling and 112 patients with SCD were genotyped for single-nucleotide polymorphisms.

MEASUREMENTS AND MAIN RESULTS

Genome-wide gene and miRNA expression profiles were correlated against TRV, yielding 631 transcripts and 12 miRNAs. Support vector machine analysis identified a 10-gene signature including GALNT13 (encoding polypeptide N-acetylgalactosaminyltransferase 13) that discriminates patients with and without increased TRV with 100% accuracy. This finding was then validated in a cohort of patients with SCD without (n = 10) and with pulmonary hypertension (n = 10, 90% accuracy). Increased TRV-related miRNAs revealed strong in silico binding predictions of miR-301a to GALNT13 corroborated by microarray analyses demonstrating an inverse correlation between their expression. A genetic association study comparing patients with an elevated (n = 49) versus normal (n = 63) TRV revealed five significant single-nucleotide polymorphisms within GALNT13 (P < 0.005), four trans-acting (P < 2.1 × 10(-7)) and one cis-acting (P = 0.6 × 10(-4)) expression quantitative trait locus upstream of the adenosine-A2B receptor gene (ADORA2B).

CONCLUSIONS

These studies validate the clinical usefulness of genomic signatures as potential biomarkers and highlight ADORA2B and GALNT13 as potential candidate genes in SCD-associated elevated TRV.

Effects of multikinase inhibitors on pressure overload-induced right ventricular remodeling

BACKGROUND

Little is known about the effects of current PAH therapies and receptor tyrosine kinase inhibitors on heart remodeling. We sought to investigate the effects of the multikinase inhibitors sunitinib (PDGFR-, VEGFR- and KIT-inhibitor) and sorafenib (raf1/b-, VEGFR-, PDGFR-inhibitor) on pressure overload induced right ventricular (RV) remodeling.

METHODS

We investigated the effects of the kinase inhibitors on hemodynamics and remodeling in rats subjected either to monocrotaline (MCT)-induced PH or to surgical pulmonary artery banding (PAB). MCT rats were treated from days 21 to 35 with either vehicle, sunitinib (1mg/kg, 5mg/kg and 10mg/kg/day) or sorafenib (10mg/kg/day). PAB rats were treated with vehicle, sunitinib (10mg/kg/day) or sorafenib (10mg/kg/day) from days 7 to 21. RV function and remodeling were determined using echocardiography, invasive hemodynamic measurement and histomorphometry.

RESULTS

Treatment with both sorafenib and sunitinib decreased right ventricular systolic pressure, pulmonary vascular remodeling, RV hypertrophy and fibrosis in MCT rats. This was associated with an improvement of RV function. Importantly, after PAB, both compounds reversed RV chamber and cellular hypertrophy, reduced RV interstitial and perivascular fibrosis, and improved RV function.

CONCLUSION

We demonstrated that sunitinib and sorafenib reversed RV remodeling and significantly improved RV function measured via a range of invasive and non-invasive cardiopulmonary endpoints in experimental models of RV hypertrophy.

Pulmonary arterial hypertension: advances in pathophysiology and management

Pulmonary arterial hypertension (PAH) is a heterogeneous, hemodynamic, and pathophysiological state which is commonly found throughout the world, but the disease burden is greater in India and in other developing countries. It is a disease characterized by vascular obstruction and vasoconstriction leading to progressive increase in pulmonary vascular resistance and right ventricular failure. PAH is a progressive disorder carrying a poor prognosis; however, dramatic progress has occurred in our knowledge of its pathogenesis and consequently, its treatment over the last two decades. In this article, we attempt to provide an overview of the etiology, pathophysiology, and current therapeutic modalities in the treatment of PAH. Patients suspected to have PAH should be submitted to a battery of investigations which help in establishing the diagnosis, identifying the etiology, guiding in treatment and informing the prognosis. All patients should be considered for standard therapy with oxygen, anticoagulation, and diuretics for right heart failure. Oral calcium channel blockers should be used in patients with a favorable response to acute vasodilator challenge. Disease targeted therapies include prostacyclines, endothelin receptor blockers, and phosphodiesterase-5 inhibitors. A brief mention of new and potential therapeutic strategies is also included.

A novel murine model of severe pulmonary arterial hypertension

RATIONALE

The complex pathologies associated with severe pulmonary arterial hypertension (PAH) in humans have been a challenge to reproduce in mice due to the subtle phenotype displayed to PAH stimuli.

OBJECTIVES

Here we aim to develop a novel murine model of PAH that recapitulates more of the pathologic processes, such as complex vascular remodeling and cardiac indices, that are not characteristic of alternative mouse models.

METHODS

Inhibition of vascular endothelial growth factor receptor (VEGFR) with SU5416 combined with 3 weeks of chronic hypoxia was investigated. Hemodynamics, cardiac function, histological assessment of pulmonary vasculature, and molecular pathway analysis gauged the extent of PAH pathology development.

MEASUREMENTS AND MAIN RESULTS

The combination of VEGFR inhibition with chronic hypoxia profoundly exacerbated all measures of PAH-like pathology when compared with hypoxia alone (> 45 mm Hg right ventricular pressure, > 0.35 right ventricular hypertrophy). The changes in pulmonary vascular remodeling in response to hypoxia were further enhanced on SU5416 treatment. Furthermore, hypoxia/SU5416 treatment steadily decreased cardiac output, indicating incipient heart failure. Molecular analysis showed a dysregulated transforming growth factor-β/bone morphogenetic protein/Smad axis in SU5416- and/or hypoxia-treated mice as well as augmented induction of IL-6 and Hif-1α levels. These changes were observed in accordance with up-regulation of Tph1 and Pdgfr gene transcripts as well as a rise in platelet-rich serotonin. Biomarker analysis in response to VEGFR inhibition and/or hypoxia revealed distinct signatures that correlate with cytokine profiles of patients with idiopathic PAH.

CONCLUSIONS

These data describe a novel murine model of PAH, which displays many of the hallmarks of the human disease, thus opening new avenues of investigation to better understand PAH pathophysiology.

Mice lacking the Raf-1 kinase inhibitor protein exhibit exaggerated hypoxia-induced pulmonary hypertension

BACKGROUND AND PURPOSE

Increased pulmonary vascular remodelling, pulmonary arterial pressure and pulmonary vascular resistance characterize the development of pulmonary arterial hypertension (PAH). Activation of the Raf/mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK)1/2 is thought to play an important role in PAH and Raf-1 kinase inhibitor protein (RKIP), negatively regulates this pathway. This study investigated whether genetic deletion of RKIP (and hence ERK1/2 up-regulation) resulted in a pulmonary hypertensive phenotype in mice and investigated a role for RKIP in mitogen-regulated proliferative responses in lung fibroblasts.

EXPERIMENTAL APPROACH

Pulmonary vascular haemodynamics and remodelling were assessed in mice genetically deficient in RKIP (RKIP-/-) after 2 weeks of either normoxia or hypoxia. Immunoblotting and immunohistochemistry were used to examine phosphorylation of Raf-1, RKIP and ERK1/2 in mouse pulmonary arteries. In vitro, RKIP inhibition of mitogen signalling was analysed in CCL39 hamster lung fibroblasts.

KEY RESULTS

RKIP-/- mice demonstrated elevated indices of PAH and ERK1/2 phosphorylation compared with wild-type (WT) mice. Hypoxic RKIP-/- mice exhibited exaggerated PAH indices. Hypoxia increased phosphorylation of Raf-1, RKIP and ERK1/2 in WT mouse pulmonary arteries and Raf-1 phosphorylation in RKIP-/- mouse pulmonary arteries. In CCL39 cells, inhibition of RKIP potentiated mitogen-induced proliferation and phosphorylation of RKIP, and Raf-1.

CONCLUSIONS AND IMPLICATIONS

The lack of RKIP protein resulted in a pulmonary hypertensive phenotype, exaggerated in hypoxia. Hypoxia induced phosphorylation of RKIP signalling elements in WT pulmonary arteries. RKIP inhibition potentiated mitogen-induced proliferation in lung fibroblasts. These results provide evidence for the involvement of RKIP in suppressing the development of hypoxia-induced PAH in mice.